Electrowetting-Based Valving and Pumping Systems

ABSTRACT

The present teachings relate to microfluidic valves and pumping systems, which may be suitable for controlling and facilitating liquid flow. Electrodes are disposed proximately to volumes containing a liquid. The liquid flow can be facilitated by electrowetting forces. Processes for controlling the flow of liquids, as well as for pumping liquids, are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/383,133, filed May 12, 2006, which claims the benefit of U.S.Provisional Application No. 60/680,889, filed May 13, 2005, all of whichare hereby incorporated in their entirety by reference.

FIELD

The present teachings relate to microfluidic valves and pumping systemssuitable for controlling and facilitating liquid flow.

INTRODUCTION

One of the challenges encountered in devices, for example, microfluidicdevices designed for high throughput operations, is effective control offluid flow, for example liquid flow. Pumps may be an important aspect ofmicrofluidic devices. A diversified range of microfluidic pumps hasbeen, and continues to be, developed. It may be difficult toindividually and independently control fluid flow in thousands ofmicrochannels without requiring fabrication of sophisticated valving andpumping systems, which may substantially increase the cost ofmanufacturing microfluidic devices. Addressing and actuating individualpumps and valves in a device may be very complex. It could be desirableto devise a method for manipulating fluid flow inside a device, forexample a microfluidic device, with great flexibility and, morespecifically, employ valves and pumps that can be easily andindependently actuated. The use of such systems could make it practicalto implement a variety of devices, such as lab-on-a-chip devices.

One aspect of the present disclosure relates to an electrowetting-basedmicrofluidic valve. Such a device may be capable of reversibly meteringthe flow of an operating liquid. The valve operates by placing andremoving a fluidic physical obstruction, which may be a complete orpartial obstruction, e.g. a gas or a liquid immiscible with theoperating liquid, along a fluidic channel. When the obstruction is inplace, the flow of an operating liquid is at least partially, if notcompletely, blocked. The actuation of such a droplet or bubble may beachieved by reversibly switching the physical characteristics of thecontacting boundary from hydrophilic to hydrophobic, and vice versa.Such a change may be obtained from electrowetting.

Another aspect of the present disclosure relates to electrowetting-basedmicrofluidic pumps. The pumps can move liquids by a number of means,such as by positive-displacement reciprocation of a fluid immisciblewith the operating liquid. Another pump can employ liquid vanes thateffectively propel the operating liquid. Like the valve, the actuationof the fluidic obstruction and the operating liquid can be produced byelectrowetting.

Electrowetting (EW) and Electrowetting on Dielectric (EWOD) use electricfields to effect fluid movement by relying on the ability of electricfields to change the contact angle of the fluid on a surface that isinitially resistant to the flow of a liquid. When an electric fieldgradient is applied to a droplet on a fluid-transporting surface,different contact angles are formed between leading and recedingsurfaces of the droplet with respect to the fluid transporting surface.This imbalance in surface tension forces will produce a net force thatmoves the droplet. EWOD may be distinguished from EW in that the formerrelies upon a thin layer of a dielectric film disposed on the surface ofat least one electrode. The dielectric film provides a degree ofdielectric capacitance between at least a portion of a surface of anelectrode and the liquid. This may facilitate more precise control offluid movement, and may also minimize, if not eliminate, electrolysis.

SUMMARY

In various embodiments, the present teachings can provide a valvingsystem comprising a channel fluidly coupled to a first reservoir and asecond reservoir; a volume in fluid communication with said channel,wherein said volume is adapted to contain a fluid chosen from a gasbubble and a liquid droplet; a first electrode proximate to said volume;a second electrode proximate to said channel, wherein said first andsecond electrodes are proximate to each other; and a power sourceelectrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.

In various embodiments, the present teachings can provide a pumpingsystem comprising a first channel fluidly coupled to a first reservoirand a second reservoir, said first channel being divided into at least afirst section, a second section, and a third section; a third reservoiropening into said second section of said first channel, said thirdreservoir comprising a first chamber and a second chamber; a pluralityof electrodes comprising an electrode proximate to each of said firstsection, second section, third section, first chamber and secondchamber; and a power source electrically coupled to each electrode, thepower source being configured to provide an electrical potentialdifference at the interface between the electrode and a liquid dropletsufficient to provide a net force to move said droplet.

In various embodiments, the present teachings can provide a valvingsystem comprising a first channel fluidly coupled to a first reservoir;a second channel fluidly coupled to said first channel, said secondchannel having a first volume adapted to contain a fluid chosen from agas bubble and a liquid droplet; a second volume comprising said firstvolume and at least a portion of said first channel; a third channelfluidly coupled to said second volume, wherein said third channelcomprises at least one section; a third volume opening into said atleast one section; a fourth channel fluidly coupled to a secondreservoir; a fifth channel fluidly coupled to said first channel, saidfifth channel having a fourth volume adapted to contain a fluid chosenfrom a gas bubble and a liquid droplet; a fifth volume comprising saidfourth volume and at least a portion of said fourth channel; anelectrode proximate to each of said volumes and channels; and a powersource electrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.

In various embodiments, the present teachings can provide a pumpingsystem suitable for a microfluidic device, comprising: a deliverychannel; an intake channel; a volume fluidly connected to said deliverychannel and said intake channel; a hub extending through said volume; aplurality of electrodes proximate to said volume; and a power sourceelectrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.

In various embodiments, the present teachings can provide a pumpingsystem suitable for a microfluidic device, comprising a first reservoir;a second reservoir; a volume between the two reservoirs adapted tocontain an fluid chosen from a gas bubble and a liquid droplet; at leastone electrode proximate to said volume; a first channel and a secondchannel allowing liquid to flow between said first reservoir and saidvolume; a third channel and a fourth channel allowing liquid to flowbetween said second reservoir and said volume; and a power sourceelectrically coupled to said at least one electrode, the power sourcebeing configured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.

In various embodiments, the present teachings can provide a valvingsystem comprising a reservoir, a channel fluidly connected to saidreservoir, at least one electrode associated with said channel, saidelectrode being proximate to the intersection of said reservoir and saidchannel; and a power source electrically coupled to said at least oneelectrode, the power source being configured to provide an electricalpotential difference at the interface between the electrode and a liquiddroplet sufficient to provide a net force to move said droplet.

In various embodiments, the present teachings can provide a valvingsystem comprising a channel fluidly coupled to a reservoir; a pluralityof electrodes comprising a first electrode proximate to said channel; asecond electrode proximate to an edge of said first electrode andproximate to said reservoir; a third electrode proximate to an edge ofsaid second electrode and proximate to said reservoir; and a powersource electrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.

In various embodiments, the present teachings can provide a process forcontrolling the flow of a liquid from a reservoir to a channel, whereinsaid reservoir is fluidly connected to said channel; a first electrodeis proximate to said reservoir and the intersection of said reservoirand said channel; a second electrode is proximate to said channel and isproximate to, and in substantially the same plane as, said firstelectrode; a fluidic obstruction substantially immiscible with saidliquid is located proximate to at least one of said first and secondelectrodes; and a power source is electrically connected to said firstand second electrodes to form first and second circuits, respectively;said process comprising alternately opening and closing said circuits toalternately cause said fluidic obstruction to transit between thesurfaces of said first and second electrodes, thereby alternatelyblocking the flow of said liquid from said reservoir into said channel.

In various embodiments, the present teachings can provide a process forcontrolling the flow of a liquid from a first reservoir to a secondreservoir in an apparatus comprising a channel disposed between, and influid communication with, a first reservoir and a second reservoir; avolume between said first and second reservoirs, wherein said volumecomprises a first chamber and a second chamber, and said second chambercomprises at least a portion of said channel, and wherein one of saidfirst and second chambers comprises a fluidic obstruction substantiallyimmiscible with said liquid; a first electrode proximate to said firstchamber, and a second electrode proximate to said second chamber; and apower source electrically connected to said first and second electrodesto form a first circuit between said power source and said firstelectrode, and a second circuit between said power source and saidsecond electrode, said process comprising alternately opening andclosing said first and second circuits to cause said fluidic obstructionto transit between said first chamber and said second chamber.

In various embodiments, the present teachings can provide a process forpumping a liquid from a first volume to a second volume, comprisingproviding a fluid substantially immiscible with said liquid in a thirdvolume, wherein said third volume is disposed between, and in fluidcommunication with, said first and second volumes, and wherein saidthird volume comprises a first chamber and a second chamber; alternatelyapplying an electric current across said first and second chambers,thereby causing the fluid to alternately transit between said first andsecond chambers, thereby drawing the liquid from said first volume,through at least a portion of said third volume, and into said secondvolume.

In various embodiments, the present teachings can provide a process forpumping a liquid from a first reservoir to a second reservoir, wherein achannel fluidly connects said first reservoir to said second reservoir;a third volume comprising a first chamber and a second chamber opensinto said channel; a first electrode is proximate to said first chamber;a second electrode is proximate to, and in substantially the same planeas, said second chamber; a fluid substantially immiscible with theliquid is located in one of said first and second chambers; and a powersource is electrically connected to said first and second electrodes toform a first circuit between said power source and said first electrode,and a second circuit between said power source and said secondelectrode, said process comprising alternately opening and closing saidfirst and second circuits to cause said fluid to transit between saidfirst chamber and said second chamber, thereby drawing the liquid fromsaid first reservoir, through said channel, and into said secondreservoir.

In various embodiments, the present teachings can provide a process forpumping a liquid in an apparatus comprising a reservoir comprising afirst surface, an opposing second surface, and a hub disposed betweensaid first and second surfaces; a first channel and a second channel,each of which is in independent fluid communication with said reservoir;a plurality of electrodes disposed in substantially the same plane undersaid first surface, wherein said plurality of electrodes is arrangedaround said hub; a power source electrically connected to each of saidelectrodes; and at least one vane comprising a fluid substantiallyimmiscible with said liquid, wherein said at least one vane is disposedover at least one of said plurality of electrodes; said processcomprising alternately applying an electric current to said electrodesto cause said at least one vane to transit around said hub, therebydrawing the liquid from said first channel, into said reservoir, and outsaid second channel.

It is to be understood that both the foregoing general description andthe following description of various embodiments are exemplary andexplanatory only and are not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various embodiments. In thedrawings,

FIGS. 1A-1D illustrate a valving system according to the presentteachings.

FIGS. 2A-2B illustrate a valving system according to the presentteachings.

FIGS. 3A-3B illustrate a three-electrode valving system according to thepresent teachings.

FIGS. 4A-4B illustrate a two-electrode valving system according to thepresent teachings.

FIGS. 5A-5D illustrate a proportional valving system according to thepresent teachings.

FIGS. 6A-6B illustrate a valving system according to the presentteachings.

FIGS. 7A-7B illustrate a valving system containing an additionalchannel, according to the present teachings.

FIGS. 8A-8B illustrate valving system having a trapezoidal-shapedchamber, according to the present teachings.

FIGS. 9A-9I illustrate the operation of a microfluidic pump according tothe present teachings.

FIGS. 10A-10C illustrate various microfluidic pumps according to thepresent teachings.

FIGS. 11A-11F illustrate the operation of a microfluidic pump accordingto the present teachings.

FIGS. 12A-12I illustrate the operation of a microfluidic pump containingon-off valve elements according to the present teachings.

FIG. 13 illustrates a microfluidic pump according to the presentteachings.

FIGS. 14A-14E illustrate the operation of a rotary vane microfluidicpump according to the present teachings.

FIGS. 15A-15B illustrate the operation of a rotary vane pump where vanesare merged and split, according to the present teachings.

FIG. 16 illustrates the operation of a rotary vane pump employingmultiple vanes, according to the present teachings.

FIGS. 17A-17B illustrate a passive valve microfluidic pump according tothe present teachings.

DESCRIPTION OF VARIOUS EMBODIMENTS

Reference will now be made to various exemplary embodiments, examples ofwhich are illustrated in the accompanying drawings. Wherever possible,the same reference numbers are used in the drawings and the descriptionto refer to the same or like parts.

FIGS. 1A-1D illustrate an exemplary embodiment of anelectrowetting-based valving system as disclosed herein. The valvingsystem can be suitable for a microfluidic device. The valve comprises amain channel 10 fluidly connected to reservoirs 20 and 30. The valvecomprises chambers 50 and 60 and optional channel 40. Optional channel40 can be fluidly connected to reservoir 20 as shown, and can also oralternatively be vented to the atmosphere. Channel 40 need not bepresent when, for example, chamber 50 contains a fluidic obstructioncomprising a gas. Electrode 70 is proximate to chamber 50, and electrode80 is proximate to chamber 60. For example, the electrodes are disposedunder the surfaces of chambers 50 and 60, respectively. At least oneground electrode may be disposed on the opposite side chambers 50 and 60from said electrodes 70 and 80. A power source is electrically coupledto said electrodes.

FIG. 1A illustrates the valve in the open position. Chamber 50 is filledwith a fluidic obstruction, for example an oil droplet, immiscible withthe operating liquid, for example an aqueous liquid such as saline. Theoperating liquid is pumped from reservoir 20 to reservoir 30. In theopen position, the surface of chamber 50 is made hydrophobic byswitching electrode 70 off (no voltage differential applied at theinterface between the electrode and the liquid). At the same time, thesurface of chamber 60 is made hydrophilic by switching electrode 80 on(a sufficiently high difference in potential is applied at the interfacebetween the electrode and the liquid). The hydrophilic operating liquidis permitted to flow from reservoir 20 to reservoir 30 while thehydrophobic oil droplet remains in chamber 50.

In the closed position, and as illustrated in FIG. 1B, electrode 70 isswitched on and electrode 80 is switched off. As a result, the oildroplet moves from chamber 50 to chamber 60. Channel 40 as shownfacilitates displacement of the oil droplet by allowing operating liquidfrom chamber 50 to fill reservoir 20. In an alternative embodiment (notshown), channel 40 is vented to the atmosphere. The main channel 10 isblocked by the oil droplet in chamber 60 and the flow of operatingliquid from reservoir 20 to reservoir 30 is obstructed. The valve may bereversibly switched to the open position (FIG. 1A) by re-establishingthe initial conditions: electrode 70 is switched off and electrode 80 isswitched on.

FIG. 1C illustrates another embodiment of the present disclosure,whereby a plurality of electrodes is employed. According to oneembodiment, six electrodes are employed, all though as few as two and asmany as 1000 electrodes may be used. The hydrophobic fluidic obstructionremains in volume 50, and the aqueous operating liquid is permitted toflow from reservoir 20, through channel 10, and into reservoir 30. Byswitching on and off various combinations of electrodes, the fluidicobstruction can transit from volume 50 and into at least a portion ofchannel 10. As shown in FIG. 1D, this has the effect of partiallyblocking the flow of the operating liquid from reservoir 20. The flow ofthe operating liquid may be halted by transiting the fluidic obstructioninto channel 10 so that the channel is completely blocked.

With proper adjustments, the same principle may be used if the operatingliquid is hydrophobic. In this case, the fluidic obstruction (i.e., theliquid immiscible with the operating liquid) can be hydrophilic, whilethe actuation of the valve will occur in the reverse order. As discussedbelow, modifications to this basic design can be implemented to preventthe fluidic obstruction from escaping from the valve seat, to extend theoperation range of the valve in terms of sustained pressuredifferential, to increase its performance, etc.

FIGS. 2A-2B illustrate another embodiment of a valving system wherebyreservoir 20 is in fluid communication with channels 10, 11, and 12.Electrodes 70, 80, and 85 are proximate to the intersections of eachchannel with reservoir 20. Although FIG. 2 illustrates an embodimentcomprising three channels and three electrodes, additional channels (andassociated electrodes) can also be included. According to oneembodiment, the three electrodes are adjacent to each other, and mayhave interdigitated sawtooth outlines.

The valving system of FIG. 2 can be useful when a single reservoirdispenses liquid to multiple locations at the respective termini ofchannels 10, 11, and 12. As shown in FIG. 2A, and taking the operatingliquid to be aqueous and the fluidic obstructions to be hydrophobic,electrode 70 is switched on and electrodes 80 and 85 are switched off.The fluidic obstructions block channels 11 and 12, while the operatingliquid can flow from reservoir 20 into channel 10. In FIG. 2B,electrodes 70 and 80 are switched off, and electrode 85 is switched on.The fluidic obstruction transits to the areas over electrodes 80 and 85,thereby blocking the flow of the operating liquid into channels 10 and11. The fluidic obstruction no longer blocks channel 12, and theoperating liquid is permitted to flow from reservoir 20 and into channel12.

FIGS. 3A-3B illustrate another embodiment of a valving system inaccordance with the present disclosure, whereby channel 10 permitsfluidic communication between reservoirs 20 and 30. Electrodes 70, 80,and 85 are positioned proximate to each other and to the intersection ofreservoir 20 and channel 10. In FIG. 3A, electrodes 80 and 85 areswitched on and electrode 70 is switched off. The hydrophobic fluidicobstruction is positioned over electrode 70, and the hydrophilicoperating liquid flows from reservoir 20, through channel 10, and intoreservoir 30. In FIG. 3B, electrode 80 is switched on and electrodes 70and 85 are switched off. The fluidic obstruction transits to the areaover electrode 80, and the flow of the operating liquid into channel 10is at least partially blocked. Electrode 85 can be switched on andelectrodes 80 and 90 can be switched off. In this configuration (notshown), the fluidic obstruction would be seated in channel 10, therebyblocking flow of operating liquid to reservoir 30.

FIGS. 4A-4B illustrates yet another embodiment, whereby electrode 70 isproximate to electrode 80, which is proximate to the fluidicintersection of reservoir 20 and channel 10. When electrode 70 isswitched on and electrode 80 is switched off (as illustrated in FIG.4A), the hydrophobic fluidic obstruction blocks channel 10, therebyprohibiting the flow of the hydrophilic operating liquid from reservoir20 to reservoir 30. When electrode 70 is switched off and electrode 80is switched on, the fluidic obstruction moves out of the fluidicintersection and permits the flow of the operating liquid into channel10.

FIGS. 5A-5D illustrate an embodiment whereby a plurality of electrodesis employed to modulate the flow of an aqueous operating liquid fromreservoir 20 to reservoir 30. In FIG. 5A, the electrodes within channel10 are switched off and the hydrophobic fluidic obstruction blocks theflow of the operating liquid. As illustrated in FIGS. 5B-5D, the flow ofthe operating liquid to reservoir 30 can be gradually increased bycausing the fluidic obstruction to transit further into reservoir 20 andaway from the fluidic intersection of reservoir 20 and channel 10.

FIGS. 6A-6B illustrate a solution that may be implemented in the casethat forces, for example surface forces arising from hydrophobicboundaries (which may result from materials commonly used inmicrofluidic practice, such as PDMS and SU-8) can destabilize thefluidic obstruction, in this case an oil droplet, and draw the fluidicobstruction into optional channel 40 and/or away from electrode 80 inchannel 10. According to one embodiment, with reference to FIG. 6A, thesurfaces of channel sections 90 and 100, and optional channel 40 can bemade hydrophilic by a hydrophilic treatment, such as by silanization.According to another embodiment, additional electrodes 110, 120 and 130may be disposed under the surface of channel sections 90 and 100, andoptional channel 40. The three additional electrodes will bealternatively, or continuously, switched on to ensure the oil droplet issurrounded by hydrophilic surfaces. Alternatively, according to anembodiment whereby the operating liquid is hydrophobic and the fluidicobstruction is hydrophilic, the surfaces of channel sections 90 and 100,and channel 40 can be made hydrophobic to stabilize the location of thehydrophilic droplet. This can be accomplished by keeping electrodes 110,120, and 130 in the off position.

FIGS. 7A-7B illustrate an additional embodiment suitable for stabilizingthe oil droplet (seated in chamber 50 in FIG. 7A, and chamber 60 in FIG.7B). An additional channel 140 is fluidly connected to reservoir 20 andchamber 60, and may be used to further drain the operating liquid fromthe valve seat when the oil droplet is displaced into chamber 60. Thisembodiment is suitable whether the operating liquid is hydrophobic orhydrophilic.

Actuation of the valves disclosed herein can be facilitated by alteringthe shape of chamber 50. According to one embodiment, and as illustratedin FIG. 8A (showing an “open” valve) and FIG. 8B (showing a “closed”valve), the shape is trapezoidal. The trapezoidal shape may produce animbalance in the forces acting upon the fluidic obstruction, generallyalong its displacement. This would have the effect of accelerating themotion of the droplet both into channel 10 and into the recess.

Another aspect of the present disclosure relates to micropumps suitablefor microfluidic applications. The micropumps disclosed herein operateby positive displacement of the operating liquid, while the actuation isprovided by electrowetting principles. These devices can deliver aliquid, for example an electrolytic liquid, in single phase form(absence of air bubbles) or in a multiphase form.

The layout and operation of the pumps disclosed herein are inspired bytraditional reciprocating piston, positive-displacement pumps. Suitablecomponents of the pumps disclosed herein include valves, a pumpingchamber or array of pumping chambers disposed between the valves,electrodes to (1) actuate the liquid motion into and from the chambersand (2) operate the valve. The operation of the pumps disclosed hereincomprises a “fill” phase, during which the operating liquid is aspiredfrom the intake to fill the chamber, and the “delivery” phase, duringwhich the working fluid is delivered from the chamber. The “intake” and“delivery” valves will open and close alternatively to prevent backflowduring the two phases.

FIG. 9 illustrates the operation of a micropump disclosed herein.Reservoirs 20 and 30 are fluidly connected via channel 10, which isdivided into an inlet section 90, a center section 210, and an outletsection 100. Channel section 90 and chamber 230 can be fluidly connectedto optional air vent 40. For the purpose of illustrating the operationof this embodiment, the operating liquid is taken to be an aqueousliquid.

In FIG. 9A, the micropump is inactive—all electrodes proximate tochannel 10 and chambers 220 and 230 are switched off and channel 10 andchambers 220 and 230 are filled with air. This prevents the hydrophilicoperating fluid from spontaneously filling components of the pump, andalso prevents any undesirable flow between channel 10 and reservoir 20.

The “fill” phase begins with the opening of the intake valve (FIG. 9B).This is initiated by switching on the electrode proximate to section 90,thus changing the physical characteristics of the contacting boundaryfrom hydrophobic to hydrophilic. This change permits the operatingliquid to flow into section 90. The second step includes filling chamber220 by switching on the electrodes associated with section 210 andchamber 220 (FIG. 9C). To complete the “fill” phase (FIG. 9D), theintake valve is closed, i.e., the liquid is displaced from the intakesection (section 90) by switching off the electrode proximate to section90. Chamber 230 is subsequently filled by switching on the electrodeproximate thereto, and switching off the electrode associated withcenter section 210 (FIG. 9E).

Delivery of the liquid (FIG. 9F) begins with opening the “deliveryvalve” by switching on the electrode associated with channel section100. The liquid will then backflow from reservoir 30 into channelsection 100. The liquid in chambers 220 and 230 is then moved to section210 by switching off the electrode proximate to chamber 230 andswitching on the electrode proximate to section 210 (FIG. 9G). Theliquid is delivered to reservoir by switching off, in order, theelectrode proximate to chamber 220, the electrode proximate to channelsection 210, and the electrode proximate to channel section 100 (FIG.9I). This last operation corresponds to closing the delivery valve. Thepump is now in the initial configuration (stand-by), and the cycle canbe restarted. In various embodiments, the pump can be operated with anysequence suitable for transporting liquid from one desired location ofthe pump to another.

According to various embodiments, the performance of the pump may bealtered in a number of ways. For example, the shape of the electrodesand chambers may vary. An electrode could have the same area as thechamber with which it is associated, could be smaller or larger, and cantake different shapes. The shape of the chambers may also vary. Forexample, using a trapezoidal shape for chambers 220-230 may allow forfaster filling and emptying, and therefore a faster cycle.

In various embodiments, there is also provided a device using an arrayof chambers instead of a single chamber (FIG. 10A), which may allow fora higher capacity (amount of operating liquid pumped per unit time) ofthe pump. Chambers can also be placed on both sides of channel 10 todouble the capacity (FIG. 10B). In various embodiments, a layoutcontaining two pumps working in opposition of phase (FIG. 10C) may allowa smoother flow.

FIG. 11 illustrates an embodiment where the actuation of the hydrophilicoperating liquid is assisted by a hydrophobic liquid to provide greatercapacity and delivery pressure. In the standby position (FIG. 11A), thehydrophobic liquid is contained in chamber 220. The electrodes proximateto chamber 220, channel section 90, and channel section 100 are switchedoff, while the electrodes proximate to chamber 230 and section 210 areswitched on, effectively trapping the hydrophobic liquid in chamber 220.During the “fill” phase (FIG. 11B), the electrodes proximate to channelsections 90 and 210, and chamber 220 are switched on, and the electrodeassociated with chamber 230 is switched off. In this manner, thehydrophobic liquid transits to chamber 230 and the hydrophilic operatingliquid flows from reservoir 20, through channel sections 90 and 210, andinto chamber 220. The “fill” phase is completed by displacing theoperating liquid from intake section 90 and section 210, and fillingchamber 220 (FIG. 11C).

The delivery phase is initiated by switching on the electrodes proximateto channel sections 100 and 210, thereby allowing the operating liquidto flow from reservoir 20, through channel 10, and into reservoir 30(FIG. 11D). The electrode proximate to chamber 230 is switched on andthe electrode proximate to chamber 220 is switched off, effectivelypumping the hydrophobic liquid from chamber 230 into chamber 220,thereby displacing the operating liquid from chamber 220 into channel 10and reservoir 30 (FIG. 11E). The electrodes proximate to channelsections 210 and 100 are then switched off in that order, completing thedelivery phase into reservoir 30 (FIG. 11F). This last operationcorresponds to closing the delivery valve. The pump is now in theinitial configuration (stand-by), and the cycle can be restarted.

In various embodiments, and as illustrated in FIG. 12, the deliverypressure range of a pump may be further extended by replacing channelsections 90 and 100 with elements of the microfluidic on-off valvesshown in, for example, FIG. 1. FIG. 12A illustrates the standbyconfiguration of such a microfluidic pump. Chambers 60 and 60A arefilled with a hydrophobic liquid, and the electrodes proximate theretoare switched off. Chamber 50 contains the aqueous operating liquid, andits electrode is switched on.

The fill phase is initiated (FIG. 12B) by switching off and onelectrodes for chambers 50 and 60, respectively. The hydrophobic fluidtransits from chamber 60 to chamber 50. Electrodes proximate to channelsection 190 and chamber 220 are also switched on, allowing the operatingliquid from reservoir 20 to flow into chamber 220 (FIG. 12C). Theremaining channel sections and chambers are subsequently filled with theoperating liquid by switching on their electrodes (FIG. 12D). The fillphase is completed by moving the hydrophobic liquid from chamber 50 backto chamber 60, thereby blocking the flow of the liquid from reservoir 20(FIG. 12E).

The delivery phase is initiated by moving the hydrophobic liquid fromchamber 60A to 50A (FIG. 12F) and switching off the electrodesassociated with the channel sections in the order shown in FIGS. 12G and12H. This facilitates the flow of the operating liquid from the chambersand channel sections into reservoir 30. When the flow is complete, thepump is converted to its standby configuration (FIG. 12I).

In various embodiments, FIG. 13 illustrates a microfluidic pumpemploying features described in, for example, FIGS. 1-12. The operationof the pump illustrated in FIG. 13 is as generally described withreference to FIGS. 1-12.

In various embodiments, there is provided a pump operable byelectrowetting. The pump, which can easily be integrated in amicrofluidic chip, operates by positive displacement of an operatingliquid with moving liquid vanes, while the actuation of the vanes isprovided by EW and/or EWOD principles (the operating liquid is taken tobe an aqueous liquid for the purposes of this illustration). Such adevice is capable of delivering and metering a liquid in a single-phaseform (e.g., in the absence of air bubbles). A general design of the pumpis illustrated in FIG. 14A, which represents the pump in a stand-byconfiguration. The pump comprises an intake port 270, a delivery port280, a chamber 290 and a hub 300, all of arbitrary shape andcross-section, and array of radial or transverse electrodes 310 coveringthe entire, or at least substantially entire, chamber, and two movablevanes 320 and 330. Each vane is a fluidic obstruction, e.g., a dropletof liquid, immiscible with the operating liquid and of opposite wettingcharacteristics (the droplets are taken to be a hydrophobic liquid forthe purposes of this illustration). The actuation of the vanes, governedby EW and EWOD principles, is obtained by switching on and off in acoordinated fashion the electrical potential of the differentelectrodes.

In various embodiments, the chamber may be in a number of differentshapes. A circular chamber may allow for a more compact pump. Inaddition, the spiraling shape of the hub may favor pumping action byincreasing the actuation force and providing greater delivery pressure.This is achieved by exploiting the differential action of the surfacetension between the leading and trailing edges of the vanes. Electrodeswith slightly rounded edges may be used to increase the net pull on thevanes due to the increased curvature of the edges of the vanes.

The operation of the pump may be illustrated as follows. In the stand-byconfiguration (FIG. 14A) the two vanes act as valves by blocking theintake and delivery ports 270 and 280, respectively. This has the effectof maintaining a pressure difference between the two ports. The pumpingaction commences by synchronously advancing both vanes one step, thusopening the intake and delivery ports (FIG. 14B). Consequently, theleading vane 320 is advanced toward the delivery port 280 while thetrailing vane is not moved (FIG. 14C). This action provides both thedelivery and the filling actions. The pumping action is complete whenthe leading vane is on the electrode preceding the delivery port (FIG.14D). The final step of the sequence is the synchronous actuation ofleading and trailing vanes onto the electrodes communicating with theintake and delivery ports (FIG. 14E). At this point, the leading vanehas become the trailing vane, and vice versa. The initial standbyconfiguration is restored and the pumping cycle is completed.

In various embodiments, the liquid vanes may be merged and split duringpump operations. This design benefits from a decreased dead-volume inthe chamber and an increased pumping efficiency. In the stand-byconfiguration (FIG. 15A), the vanes are merged and split and block thedelivery. Subsequently, the vanes are moved forward by one step andsplit (FIG. 15B). The pumping cycle at this point is the same as thepumping cycle described with reference to FIG. 14 with the exceptionthat at the end of the forward actuation, the leading vane meets thetrailing vane and merges with it.

In various embodiments, more than two vanes of immiscible droplets maybe used. FIG. 16 illustrates a design employing four vanes. The arrowsin the figure demonstrate the movement of the operating liquid into theintake port, through the pump, and out the delivery port. The use of,e.g., four vanes may improve both the control and the delivery speed ofthe pump.

In various embodiments, there is provided an EW-based passive-valvemicrofluidic pump. The operation of the pump, which may be integratedinto a microfluidic device, is based on the combined action of anEW-actuated liquid piston in a pumping chamber and of microfluidicelements with preferential flow direction acting as passive injectorsand passive valves.

The pump, illustrated in FIG. 17A, comprises a volume subdivided intochambers 50 and 60. Electrodes 70 and 80 are proximate to chambers 50and 60, respectively. Chamber 50 houses a liquid droplet, for example anoil droplet, immiscible with the aqueous operating liquid. The pumpfurther comprises valves 340 and 350, and injectors 360 and 370. Each ofthe valves and injectors may be shaped in such a way that the flowresistance is larger for the flow in one direction relative to theopposite direction. In other words, for a given pressure drop, there isa larger flowrate when the pressure drop is applied in one direction,and a smaller flowrate for the opposite direction. A design consistingof a smooth contraction followed by a sudden expansion generates lessresistance to a flow passing through it relative to a sudden contractionfollowed by a smooth expansion. If two such fluidic elements are placedin parallel and with opposite orientation, one may act as an “injector”and the other as a “valve.”

In various embodiments, the first stroke of the two-stroke cycle isillustrated in FIG. 17A. Electrode 80 is switched on and electrode 70 isswitched off. As a result, the hydrophobic liquid piston moves fromchamber 60 to chamber 50. In this motion, it will displace the aqueousoperating liquid out of chamber 50. Due to the valve-injectorconfiguration of its adjacent fluidic elements, a larger amount of theoperating liquid will flow to reservoir 30 than reservoir 20, resultingin a net flowrate to reservoir 30. At the same time, the motion of theliquid piston will withdraw liquid from reservoir 20 into chamber 60.The valve-injector configuration results in a net flowrate intoreservoir 20. As a result, at the end of the stroke a net positiveflowrate of working liquid will have occurred between reservoirs 20 and30.

In the second stroke (FIG. 17B), electrode 70 is switched on andelectrode 80 is switched off, causing a reverse motion of the liquidpiston. Relative to the first stroke, the function of the fluidicelements is reversed from “injector” to “valve,” and vice versa.However, due to symmetry, the resulting effect is still a net positiveflowrate from the intake to delivery.

In various embodiments, the valving and pumping systems disclosed hereinmay operate with an operating liquid and a fluidic obstruction. The twoare suitable immiscible with each other. Examples of operatingliquid/fluidic obstruction pairs include hydrophilic and hydrophobicliquids, such as oil and saline. In another embodiment, the devicesdisclosed herein may operate with a liquid in combination with a volumeof gas, for example air or an inert gas such as nitrogen.

In various embodiments, the valves and pumps disclosed herein may beoperable with any fluid, for example a liquid, which is capable of beingmanipulated by electrowetting forces. For example, the devices may beused to manipulate a biological liquid. The term “biological liquid” asused herein refers to liquids comprising biomolecules, for examplenucleic acids, peptides, and enzymes, and also refers to liquidscontaining bioparticles, for example cells, organelles, etc.

Liquids, including biological liquids that are electrolytic, may be usedin the valving and pumping systems according the present teachings. Theterm “electrolytic” refers to a liquid containing substances dissolvedtherein, such as ionic salts, which enable the liquid to conducting anelectric current. By way of non-limiting example, other liquids that maybe used in the valving and pumping systems according to the presentteachings can include aqueous liquids, such as water and bufferedsaline, as well as non-aqueous liquids such as dimethylsulfoxide,acetone, acetonitrile, and other non-aqueous solvents. For example, theaqueous and non-aqueous liquids may include, e.g., rinsing solutions.

Ionic liquids may also be used in the valving and pumping systemsaccording to the present invention. “Ionic liquids” refers to salts thatare liquid over a wide temperature range, including room temperature.The liquid can include various substances, particulate and otherwise.Such substances may include, for example, surfactants, includinganionic, nonionic, cationic, and amphoteric surfactants. The compositionof the liquid, including the presence of surfactants, biomolecules, andother substances, may influence the surface wetting, and thus thecontact angle, of the liquid.

In various embodiments, channels suitable for use in accordance with thepresent invention include any volume through which a liquid may betransported. Suitable channels may be made of glass, and may optionallybe transparent, or at least partially transparent, when employed inlight-actuated valves and pumps. The channels may be constructed of anymaterial suitable for containment of a given liquid, for example glassor a polymeric material. The channels may of any dimension suitable formanipulating liquids in a desired manner. For example, according tovarious embodiments, the length, width and depth of the channels mayrange, independently, from 0.1 μm to 10 cm, for example, 10 μm to 1 cm.

In various embodiments, reservoirs suitable for use in the pumps andvalves disclosed herein include any space capable of containing a liquidand communicating with at least one channel and/or additional reservoir.The reservoirs can, in practice, be any volume capable of containing aliquid such as, for example, fluidic manifolds, fluid reservoirs, ducts,channels, wells, etc. For example, the reservoirs may independently bechannels fluidly connected to at least one other microfluidic device ordetection element. The reservoirs may be constructed of any materialcapable of holding a liquid, for example glass or a polymer. Thereservoir may be of any shape and of any cross section, for example itmay be spherical, semi-spherical, or conical. The reservoir may be ofany size sufficient to hold the desired volume of liquid. For example,the reservoir may range in size from 1 nanoliter to 1 liter.

In various embodiments, chambers suitable for use in the presentdisclosure include any space capable of containing a liquid andcommunicating with at least one channel and/or additional chamber.Typically, the chambers disclosed herein will be associated with atleast one electrode capable of applying an electrical potentialdifference at the solid/liquid interface of the chamber. Like thereservoirs, the chambers may be constructed of any material capable ofholding a liquid, for example glass, a polymer, and laminated structurescomprising different materials. In various embodiments, the chamber mayoptionally be transparent, or at least partially transparent, whenemployed in light-actuated valves and pumps. The chamber may be of anyshape, for example it may be spherical, semi-spherical, trapezoidal, ortriangular. The chamber may be of any size sufficient to hold thedesired volume of liquid. For example, the chamber may range in sizefrom 1 nanoliter to 1 centiliter.

The electrodes may be of any material and dimensions suitable for movinga fluid by electrowetting. For example, the electrodes may be thin metalfilms, patterned using any thin film deposition process known in theart. The electrodes may be made from any conductive material such as,for example, copper, gold, platinum, aluminum, and conducting polymers,including polymers that are conducting per se, and conducting compositescontaining a non-conducting polymer and a conducting material such as ametal or a conducting polymer. The electrodes may be of any dimensionsuitable for transporting a liquid by EW or EWOD. For example, theelectrodes may range in size from 10 μm to 5 mm on each side. In variousembodiments, the edges of the electrodes have interdigitated sawtooth ormeander outlines. In various embodiments, the electrode may betransparent. By way of example, the electrode may be formed oftransparent indium tin oxide.

In various embodiments, the electrodes are provided as a two-dimensionalmatrix array. Such an array allows movement of the fluids byelectrowetting in any direction on the substrate. The matrix array maycomprise 4 to 10,000 individually addressable electrodes. The electrodesmay be flush, or may be spaced apart by a gap. The gap may range in sizefrom 1 μm to 2 mm. The valving and pumping systems disclosed herein maycontain a volume formed by two opposing, or at least substantiallyopposing, surfaces. One surface may contain an electrode, or array ofelectrodes, and the opposing surface may comprise a ground electrode.

An insulating layer may be inserted at the interface between the dropletand the electrode to accommodate a high applied voltage withoutelectrolysis. In various embodiments, the insulating layer is comprisedof any material capable of electrically insulating the electrode.Depending on the choice of materials, it may be advantageous for theelectrically insulative layer to also be chemically insulative. Thechemically insulative layer may function to protect the surface frompotentially corrosive effects of a liquid. According to variousembodiments, it could be advantageous for the insulative layer to bemade hydrophobic. This may be accomplished by selecting a hydrophobicinsulative layer. Alternatively, it may be accomplished by making theinsulative layer hydrophobic by, for example, binding a hydrophobicmoiety to the surface. Exemplary hydrophobic moieties include silanes,siloxanes, fluorosilanes, fluorosiloxanes, hydrocarbons, fluorocarbons,combinations thereof, and polymers and copolymers of any of theforegoing. Those of ordinary skill in the art will appreciate that theselection of an appropriate insulative layer may depend on the choice ofoperating liquid for which the device is to be used.

Any material capable of providing an electrically and/or chemicallyinsulative layer may be used in accordance with various embodiments. Forexample the insulating layer may be comprised of silicon oxide, siliconnitride, silicon oxynitride, tantalum oxide, polymers such as Parylene,Dupont Teflon AF, 3M Fluorad, 3M EGC 1700, other fluoropolymers,polysiloxanes, and carbon. The thickness of the insulative layer mayrange from 0.1 μm to about 200 μm.

In various embodiments, the electrodes and/or insulative coatingsthereon may be textured as a way of potentially manipulating chargedensity. For example, the topography of the surfaces may be altered. Thesurface modification may involve increasing or decreasing surfaceroughness. Such modifications may be conducted by any known additive orsubtractive methods, including depositioning, masking, and etchingprocesses.

In various embodiments, the power source may be chosen from any sourcesuitable for providing a sufficient electrical potential differenceacross a liquid in a channel or a chamber. According to one embodiment,the power source is configured to provide a direct current. According toanother embodiment, for example in the case of optoelectronic devices,the power source is configured to provide an alternating current. Thevoltage and frequency characteristics may be chosen according to thematerials used in the valving and pumping systems disclosed herein. Themagnitude of the voltage source can vary according to the properties,e.g., the thickness, of the materials used to construct the device. Invarious embodiments, the voltage source can supply an electricalpotential difference ranging from 10 volts to several hundred volts. Inthe case of an AC source, the frequency can range from 10 Hz to 500 kHz.In one embodiment, the voltage source is connected to the valve withonly two leads. In another embodiment, the voltage source is inductivelyconnected such that no electrical leads are required.

In various embodiments, liquids may be manipulated in the valves andpumps disclosed herein by optical activation with directed light.Optical activation may eliminate the need for individually addressedelectrodes. In such an embodiment, a photoconductive material iselectrically connected to both an electrode and the insulative coating.For example, the photoconductive material is disposed between theelectrode and the insulative coating. The photoconductive material isactivatable by directed light to provide an electrical potentialdifference across the insulating layer.

In various embodiments, the photoconductive material useful in thevalves and pumps disclosed herein corresponds to a material with a darkconductivity ranging from 10⁻⁵ to 10⁻¹² Ω⁻¹·cm⁻¹. The photoconductivematerial exhibits relatively low conductivity when dark, and relativelyhigh conductivity when illuminated by a light source. In variousembodiments, an example of a suitable photoconductive material isamorphous silicon, which has a dark conductivity of approximately 10⁻⁸Ω⁻¹·cm⁻¹. In various embodiments, light with a wavelength ranging from400 nm to 1100 nm is used to illuminate at least portions of theamorphous silicon. The light intensity for activating the gas-samplingdevice can be low. For example, a light intensity that may be suitablefor switching amorphous silicon is 65 mW/cm². The layer ofphotoconductive material permits optical control of an electricalpotential difference across a corresponding portion of the device.Optical activation of EW and EWOD devices is further discussed in U.S.Provisional Application No. 60/642,828, filed Jan. 11, 2005, thedisclosure of which is incorporated herein by reference in its entirety.

According to various embodiments, the present teachings provide pumpingsystem including a first channel fluidly coupled to a first reservoirand a second reservoir, said first channel being divided into at least afirst section, a second section, and a third section; a third reservoiropening into said second section of said first channel, said thirdreservoir including a first chamber and a second chamber; a plurality ofelectrodes including an electrode proximate to each of said firstsection, second section, third section, first chamber and secondchamber; and a power source electrically coupled to each electrode, thepower source being configured to provide an electrical potentialdifference at the interface between the electrode and a liquid dropletsufficient to provide a net force to move said droplet. The system canhave at least one dimension of said first and second chambers of saidthird reservoir is triangular in shape. The system can also include anair vent fluidly coupled to at least one of said first channel, saidfirst reservoir, and said third reservoir The system can also include afluid in said first chamber, wherein said fluid is at leastsubstantially immiscible with a liquid to be pumped by said system. Thesystem can have said first channel is further divided into at least oneadditional section; said system contains at least one additionalreservoir opening into said at least one additional section of saidfirst channel; said at least one additional reservoir includes a firstchamber and a second chamber; at least one electrode is proximate toeach of at least one additional section of said first channel, and saidfirst and second chambers of said at least one additional reservoir; andsaid at least one electrode is electrically coupled to said powersource. The system can have at least one additional reservoir ispositioned on the opposite side of said first channel from said thirdreservoir. The system can have a photoconductive material iselectrically coupled to at least one of said electrodes. The system canalso include a second channel fluidly coupled to said first reservoirand said second reservoir, said second channel being divided into atleast a first section, a second section, and a third section; a fourthreservoir opening into said second section of said second channel, saidfourth reservoir including a first chamber and a second chamber; and aplurality of electrodes including an electrode proximate to each of saidfirst second, and third sections of said second channel and said firstand second chambers of said fourth reservoir; wherein said plurality ofelectrodes is electrically connected to said power source.

According to various embodiments, the present teachings provide apumping system suitable for a microfluidic device including a deliverychannel; an intake channel; a volume fluidly connected to said deliverychannel and said intake channel; a hub extending through said volume; aplurality of electrodes proximate to said volume; and a power sourceelectrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet. The system can have saidvolume has a circular shape. The system can have said hub has a spiralshape. The system can have said electrodes have at least one circularedge. The system can have said volume is bounded by a first surface andan opposed and parallel second surface. The system can have said firstsurface includes said plurality of electrodes. The system can have aphotoconductive material is electrically coupled to at least one of saidelectrodes.

According to various embodiments, the present teachings provide apumping system suitable for a microfluidic device including a firstreservoir; a second reservoir; a volume between the two reservoirsadapted to contain an fluid chosen from a gas bubble and a liquiddroplet; at least one electrode proximate to said volume; a firstchannel and a second channel allowing liquid to flow between said firstreservoir and said volume; a third channel and a fourth channel allowingliquid to flow between said second reservoir and said volume; and apower source electrically coupled to each electrode, the power sourcebeing configured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet. The system can have at leastone of said channels has a triangular dimension. The system can have atleast one of said channels is conical in shape. The system can have eachof said channels is conical in shape. The system can have said volumeincludes a first chamber and a second chamber. The system can have saidvolume includes a first surface and an opposing, parallel secondsurface. The system can have said second surface includes a groundelectrode. The system also including a liquid disposed in one of saidfirst and second chambers, wherein said liquid is substantiallyimmiscible with a liquid to be pumped by said system. The system canhave a photoconductive material is electrically coupled to at least oneof said electrodes.

According to various embodiments, the present teachings provide aprocess for controlling the flow of a liquid from a reservoir to achannel, wherein: said reservoir is fluidly connected to said channel; afirst electrode is proximate to said reservoir and the intersection ofsaid reservoir and said channel; a second electrode is proximate to saidchannel and is proximate to, and in substantially the same plane as,said first electrode; a fluidic obstruction substantially immisciblewith said liquid is located proximate to at least one of said first andsecond electrodes; and a power source is electrically connected to saidfirst and second electrodes to form first and second circuits,respectively; said process including alternately opening and closingsaid circuits to alternately cause said fluidic obstruction to transitbetween the surfaces of said first and second electrodes, therebyalternately blocking the flow of said liquid from said reservoir intosaid channel. The process can have said first and second electrodes haveadjoining edges. The process can also include at least one groundelectrode in spatial opposition to said first and second electrodes. Theprocess can have said liquid is a hydrophilic liquid and said fluidicobstruction is a hydrophobic liquid droplet. The process can have saidliquid is a hydrophobic liquid and said fluidic obstruction is ahydrophilic liquid droplet. The process can have closing the circuit tothe first electrode and opening the circuit to the second electroderesults in the movement of the fluidic obstruction away from the firstelectrode and towards the second electrode. The process can have openingthe circuit to the first electrode and closing the circuit to the secondelectrode results in the movement of the fluidic obstruction away fromthe second electrode and towards the first electrode. The process canhave a photoconductive material is electrically connected to at leastone of said first and second circuits, and wherein said at least onecircuit is alternately opened and closed by alternately directing lightupon said photoconductive material.

According to various embodiments, the present teachings provide aprocess for controlling the flow of a liquid from a first reservoir to asecond reservoir in an apparatus including a channel disposed between,and in fluid communication with, a first reservoir and a secondreservoir; a volume between said first and second reservoirs, whereinsaid volume includes a first chamber and a second chamber, and saidsecond chamber includes at least a portion of said channel, and whereinone of said first and second chambers includes a fluidic obstructionsubstantially immiscible with said liquid; a first electrode proximateto said first chamber, and a second electrode proximate to said secondchamber; and a power source electrically connected to said first andsecond electrodes to form a first circuit between said power source andsaid first electrode, and a second circuit between said power source andsaid second electrode, said process including alternately opening andclosing said first and second circuits to cause said fluidic obstructionto transit between said first chamber and said second chamber. Theprocess can have the flow of the liquid from the first reservoir to thesecond reservoir is blocked when the fluidic obstruction is in saidsecond chamber. The process can also include at least one groundelectrode in spatial opposition to said first and second electrodes. Theprocess can have said liquid is a hydrophilic liquid, and said fluidicobstruction is a hydrophobic liquid droplet. The process can have saidliquid is a hydrophobic liquid and said fluidic obstruction is ahydrophilic liquid droplet. The process can have closing the circuit tothe first electrode and opening the circuit to the second electroderesults in the movement of the fluidic obstruction from the firstchamber into the second chamber. The process can have opening thecircuit to the first electrode and closing the circuit to the secondelectrode results in the movement of the fluidic obstruction from thesecond chamber into the first chamber. The process can have wherein aphotoconductive material is electrically connected to each of said firstand second circuits, and wherein the first and second circuits arealternately opened and closed by alternately directing light upon saidphotoconductive material.

According to various embodiments, the present teachings provide aprocess for pumping a liquid from a first volume to a second volumeincluding providing a fluid substantially immiscible with said liquid ina third volume, wherein said third volume is disposed between, and influid communication with, said first and second volumes, and whereinsaid third volume includes a first chamber and a second chamber;alternately applying an electric current across said first and secondchambers, thereby causing the fluid to alternately transit between saidfirst and second chambers, thereby drawing the liquid from said firstvolume, through at least a portion of said third volume, and into saidsecond volume. The process can have said liquid is a hydrophilic liquid,and said fluid is a hydrophobic liquid droplet. The process can havesaid liquid is a hydrophobic liquid and said fluid is a hydrophilicliquid droplet. The process can have said electric current isalternately applied across said first and second chambers by opticalactivation of a photoconductive material.

According to various embodiments, the present teachings provide aprocess for pumping a liquid from a first reservoir to a secondreservoir, wherein: a channel fluidly connects said first reservoir tosaid second reservoir; a third volume including a first chamber and asecond chamber opens into said channel; a first electrode is proximateto said first chamber; a second electrode is proximate to, and insubstantially the same plane as, said second chamber; a fluidsubstantially immiscible with the liquid is located in one of said firstand second chambers; and a power source is electrically connected tosaid first and second electrodes to form a first circuit between saidpower source and said first electrode, and a second circuit between saidpower source and said second electrode, said process includingalternately opening and closing said first and second circuits to causesaid fluid to transit between said first chamber and said secondchamber, thereby drawing the liquid from said first reservoir, throughsaid channel, and into said second reservoir. The process can alsoinclude at least one ground electrode in spatial opposition to saidfirst and second electrodes. The process can have said liquid is ahydrophilic liquid, and said fluid is a hydrophobic liquid droplet. Theprocess can have said liquid is a hydrophobic liquid and said fluid is ahydrophilic liquid droplet. The process can have closing the circuit tothe first electrode and opening the circuit to the second electroderesults in the movement of the fluid from the first chamber and into thesecond chamber. The process can have opening the circuit to the firstelectrode and closing the circuit to the second electrode results in themovement of the fluid from the second chamber and into the firstchamber. The process can have a photoconductive material is electricallyconnected to said first and second circuits, and wherein the first andsecond circuits are opened and closed by alternately directing lightupon said photoconductive material.

According to various embodiments, the present teachings provide aprocess for pumping a liquid in an apparatus including a reservoirincluding a first surface, an opposing second surface, and a hubdisposed between said first and second surfaces; a first channel and asecond channel, each of which is in independent fluid communication withsaid reservoir; a plurality of electrodes disposed in substantially thesame plane under said first surface, wherein said plurality ofelectrodes is arranged around said hub; a power source electricallyconnected to each of said electrodes; and at least one vane including afluid substantially immiscible with said liquid, wherein said at leastone vane is disposed over at least one of said plurality of electrodes;said process including alternately applying an electric current to saidelectrodes to cause said at least one vane to transit around said hub,thereby drawing the liquid from said first channel, into said reservoir,and out said second channel. The process can also include at least oneground electrode in spatial opposition to said plurality of electrodes.The process can have said liquid is a hydrophilic liquid, and said fluidis a hydrophobic liquid droplet. The process can said liquid is ahydrophobic liquid and said fluid is a hydrophilic liquid droplet. Theprocess can have the apparatus further includes a photoconductivematerial electrically connected to said power source and said pluralityof electrodes, and the electric current is applied by directing lightupon said photoconductive material.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all subranges subsumedtherein. For example, a range of “less than 10” includes any and allsubranges between (and including) the minimum value of zero and themaximum value of 10, that is, any and all subranges having a minimumvalue of equal to or greater than zero and a maximum value of equal toor less than 10, e.g., 1 to 5.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” include plural referents unlessexpressly and unequivocally limited to one referent. Thus, for example,reference to “a charged species ” includes two or more different chargedspecies. As used herein, the term “include” and its grammatical variantsare intended to be non-limiting, such that recitation of items in a listis not to the exclusion of other like items that can be substituted oradded to the listed items.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to various embodimentsdescribed herein without departing from the spirit or scope of thepresent teachings. Thus, it is intended that the various embodimentsdescribed herein cover other modifications and variations within thescope of the appended claims and their equivalents.

1. A valving system comprising: a channel fluidly coupled to a firstreservoir and a second reservoir; a volume in fluid communication withsaid channel, wherein said volume is adapted to contain a fluid chosenfrom a gas bubble and a liquid droplet; a first electrode proximate tosaid volume; a second electrode proximate to said channel, wherein saidfirst and second electrodes are proximate to each other; and a powersource electrically coupled to each electrode, the power source beingconfigured to provide an electrical potential difference at theinterface between the electrode and a liquid droplet sufficient toprovide a net force to move said droplet.
 2. The system according toclaim 1 further comprising a second channel, wherein said second channelis at least one of vented to the atmosphere, fluidly coupled to saidvolume, fluidly coupled to said first reservoir, fluidly coupled to saidsecond reservoir, fluidly coupled to another fluidic component, andblind.
 3. The system according to claim 1, wherein said first and secondelectrodes have adjoining edges.
 4. The system according to claim 1,wherein at least a portion of the channel is hydrophilic.
 5. The systemaccording to claim 1, wherein at least a portion of the channel ishydrophobic.
 6. The system according to claim 1, further comprising atleast one additional electrode in said channel.
 7. The system accordingto claim 2, further comprising an electrode proximate to at least aportion of said second channel.
 8. The system according to claim 2,further comprising a third channel.
 9. The system according to claim 8,wherein said third channel is fluidly coupled to said first channel andat least one of the atmosphere, said first reservoir, said secondreservoir, and an additional fluidic component.
 10. The system accordingto claim 1, wherein at least one dimension of at least a portion of saidvolume is trapezoidal in shape.
 11. The system according to claim 8,wherein at least one dimension of at least a portion of said volume istrapezoidal in shape.
 12. The system according to claim 1, wherein aphotoconductive material is electrically coupled to at least one of saidfirst and second electrodes. 13-28. (canceled)